Transmission apparatus and base station apparatus using the same

ABSTRACT

The transmission apparatus according to the present invention includes a switching device that switches the multiplexing destination of mask symbols and uses this switching device to switch the multiplexing destination of the mask symbols so that the mask symbols multiplexed with control channel signals transmitted in parallel from a plurality of antennas may be transmitted from only one antenna at each transmission timing.

This is a continuation of application Ser. No. 09/321,857, filed May 28,1999 now U.S. Pat. No. 6,519,238.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to transmission apparatuses used in radiocommunication systems and base station apparatuses using them.

2. Description of the Related Art

CDMA (Code Division Multiple Access) has been developed as a multipleaccess system used in next generation mobile communication systems. Inthis CDMA cellular system, it is necessary to make a cell search forestablishing initial synchronization when a mobile station turns onpower or for cell switching (handover) when traveling.

Regarding the cell search method in this CDMA cellular system, asdescribed in “Fast Cell Search Algorithm using Long Code Masking inDS-CDMA Asynchronous Cellular Systems” by Higuchi, Sawabashi, Adachi, etal., in TECHNICAL REPORT OF IEICE (RCS96-122, 1997-01), a method isproposed by which long codes of downlink control channels are masked andcorrelation detection is performed on these masked parts using shortcodes which are common to cells to detect the timing and type of thelong codes.

According to this system, the transmitting side (base station)code-multiplexes symbols spread using a short code (CSC) which is commonto cells and symbols spread using a long code group identification shortcode (GIC), with the long code masked part and transmits them, and thereceiving side (mobile station) detects the timings by the short codewhich is common to cells, then limits long code candidates to besearched for by a long code identification section using the long codegroup identification short codes and specifies the cell-specific longcodes from among these long code candidates, achieving a fast cellsearch. The above two short codes(CSC and GIC) are codes for search,called search codes hereinafter.

Furthermore, the transmitting side is provided with a plurality oftransmission antennas per sector, and if control channel signals arespread using different short codes and each transmitted in parallel froma plurality of antennas, the control channel signals become moreresistant to fading variations (especially during slow movement) andshadowing due to a transmission diversity effect, improving theirreception characteristics.

In general, during parallel transmission, a same long code is used for aplurality of antennas and their transmission power is determined takingaccount of interference with other channels or other cells as follows:if transmission is performed with power of 1 through one antenna, thenthrough two antennas transmission is performed with power of 0.5 each.At this time, the transmission characteristic of each antennadeteriorates by the degree transmission power is weakened, but adiversity effect produced when the receiving side combines a pluralityof transmission signals improves reception characteristics in the longrun.

However, in the cell search method above, if a same search code istransmitted from a plurality of antennas simultaneously, the number ofmatched filters will not increase on the receiving side but receptioncharacteristics deteriorate due to independent fading variations. On theother hand, using different short codes (search codes) like controlchannels will cause problems such as code shortage or deterioration ofreception characteristics due to an increase of the number of matchedfilters or increase of interference (mutual correlation between searchcodes) on the receiving side.

SUMMARY OF THE INVENTION

It is an objective of the present invention to provide a transmissionapparatus and base station apparatus using it, capable of preventingdeterioration of reception characteristics during a cell search on thereceiving side due to fading variations or an increase of the number ofmatched filters and interference even when the transmitting sidetransmits control channel signals in parallel from a plurality ofantennas.

A technology of transmitting signals in parallel from a plurality ofantennas (parallel transmission) is being studied in radio communicationsystems. Suppose this parallel transmission includes all transmissionsystems simply carrying out parallel transmission from a plurality ofantennas without depending on the transmitting order or timing oftransmission signals or spreading codes. Recently, introducing anorthogonal transmission diversity system (OTD) using a plurality ofantennas in CDMA radio communication systems is under study. Thistechnology is intended to effectively improve reception characteristicsthrough transmission diversity effects.

Thus, the present inventor, et al. came up with the present invention bytaking notice of introducing a parallel transmission technology to cellsearches in the CDMA cellular system and finding that its transmissiondiversity effect improves reception characteristics. This allowstransmitted/received signals to become more resistant to fadingvariations (especially during slow movement) or shadowing, improvingreception characteristics.

The present inventor, et al. also came up with the present invention byfinding that applying the OTD technology to control channels, forexample, perch channels, would improve reception characteristics throughdiversity effects. This makes it possible to extend the cell radius(coverd area) while using same transmission power and suppressinterference with other channels due to a reduction of perch channeltransmission power in the same area.

That is, the key point of the present invention is TSDT (Time-SwitchedTransmit Diversity) which means when carrying out diversitytransmission, control channels (CCH) are transmitted in parallel througha plurality of antennas with search codes inserted and by switchingthose antennas according to the search codes.

More specifically, antennas transmitting search codes are switched sothat a search code may be transmitted through only one antenna in agiven instant. In this case, switching of antennas can be performedeither periodically or randomly. In other words, it is only search codesthat are transmitted using TSTD. When a plurality of search codes aremultiplexed and transmitted, either they may always be multiplexed andsent from a same antenna or they may be transmitted from differentantennas. Transmission using a same antenna is necessary when using onecode to detect another data-modulated code.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the invention will appearmore fully hereinafter from a consideration of the following descriptiontaken in connection with the accompanying drawing wherein one example isillustrated by way of example, in which;

FIG. 1 is a block diagram showing the configuration of an apparatuscarrying out parallel transmission in a base station apparatus accordingto Embodiment 1 of the present invention;

FIG.B 2 is a block diagram showing the configuration of an apparatuscreating long code masks of the base station apparatus according to theabove embodiment;

FIG. 3 is a block diagram showing the configuration of a transmissionapparatus of the base station apparatus according to the aboveembodiment;

FIG. 4 is a block diagram showing the configuration of an apparatuscarrying out orthogonal transmission diversity in a base stationapparatus according to Embodiment 2 of the present invention;

FIG. 5 is a block diagram showing the configuration of a transmissionapparatus of the base station apparatus according to the aboveembodiment;

FIG. 6 is a schematic drawing showing the configuration of a search codemultiplexing section of the transmission apparatus of Embodiments 1 and2 above;

FIG. 7 is a schematic drawing showing the configuration of a search codemultiplexing section of the transmission apparatus of Embodiments 1 and2 above;

FIG. 8 is a schematic drawing showing the timing of multiplexing searchcodes with control channels in Embodiments 1 and 2 above;

FIG. 9 is a schematic drawing showing the timing of multiplexing searchcodes with control channels in Embodiments 1 and 2 above;

FIG. 10 is a block diagram showing the configuration of a transmissionapparatus of a base station apparatus according to Embodiment 3 of thepresent invention;

FIG. 11 is a drawing to explain the timing of multiplexing search codeswith control channels in Embodiment 3 above;

FIG. 12 is a drawing to explain the multiplexing timing when controlchannels and search code channels are code-multiplexed in Embodiment 3above; and

FIG. 13 is a drawing to explain the multiplexing timing when controlchannels and search code channels are code-multiplexed in Embodiment 3above.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference now to the attached drawings, the embodiments of thepresent invention are explained in detail below.

(Embodiment 1)

First, FIG. 1 is used to explain parallel transmission. FIG. 1 is ablock diagram showing the configuration of an apparatus carrying outparallel transmission in a base station apparatus according toEmbodiment 1 of the present invention. This apparatus modulatestransmission data through a plurality (two in the figure) of datamodulation sections 101,102, spreads through spreading-modulationsections 103,104, carries the data on carriers through radiotransmission circuits 105,106 and transmits through antennas 107, 108.

Then, FIG. 2 is used to explain how a long code mask is created. FIG. 2is a block diagram showing the configuration of an apparatus creatinglong code masks in the base station apparatus according to Embodiment 1of the present invention. In this apparatus, a control channel signal ismodulated by data modulation circuit 201, and these modulated data aremultiplied in multiplier 203 by short code SC0 and long code LCj whichwere multiplied by multiplier 202 beforehand.

For the part to be masked in a control channel signal, short code CSC(first search code) and group identification code GICJ (second searchcode) are added up. These short code CSC and group identification codeGICJ are added to the control channel signal as masks after they areappropriately switched by switch 205 according to mask control signal206 having a pulse waveform shown in the figure.

Then, the transmission apparatus of the present embodiment is explainedusing FIG. 3. FIG. 3 is a block diagram showing the configuration of thetransmission apparatus of the base station apparatus according to theabove embodiment.

This transmission apparatus enables parallel transmission using twosystems and comprises data modulation circuits 301,302 that carry outdata modulation, multipliers 304,306 that multiply the demodulatedsignals by specific codes, multipliers 303,305 that multiply long codeLCj (scrambling code) and short codes SC0,SC1 respectively, a searchcode providing section that provides search codes, and a search codemultiplexing section that multiplexes the search codes using switches308,309,310 which are the sections for Switching the multiplexingdestinations of search codes.

As shown in FIG. 6, the search code providing section comprises adder307 that adds up short code CSC and group identification code CICj andthe search code multiplexing section comprises switches 308,309,310 thatmultiplex the added codes over one control channel signal as a mask.

Then, the operation of the transmission apparatus configured as shownabove is explained.

Control channel signals are each input to data modulation circuits301,302 where they are subjected to data-modulation processing. Inmultipliers 303,305, long code LCj and short codes SC0, SC1 aremultiplied. These multiplied long code LCj and short code SC0 aremultiplied on the output of data modulation circuit 301 by multiplier304 and long code LCj and short code SC1 are multiplied on the output ofdata modulation circuit 302 by multiplier 306.

In a base station apparatus provided with this transmission apparatus,for example, a long code LCj assigned differs from one base station toanother. As described above, control channel signals are dually spreadwith long code LCj and short code SC. This allows each base station touse a common short code group.

On the other hand, in the search code providing section, short code CSCand group identification code GICj are added up by adder 307 and themultiplexing section multiplexes them over one control channel signal byswitching of switch (TSW) 308. Switching of switch 308 is controlled bytransmission antenna switching control signal 311.

Switch (SW0) 309 and switch (SW1) 310 turn ON at a prescribed timing andaforementioned short code CSC and group identification code GICj aremultiplexed over a control channel signal at that timing.

Therefore, if switch TSW 308 turns ON at a timing of the waveform inFIG. 3, that is, it is selected as the multiplexing destination,switches SW0 and SW1 turn ON at a timing of the waveform in FIG. 3 andshort code CSC and group identification code GICJ are multiplexed overthe control channel signal. These switches SW0 and SW1 are controlled bymask control signal 312. That is, switches SW0,SW1 are controlled sothat short code CSC and group identification code GICj may bemultiplexed over one control channel signal at a specific timing.

Such control allows a search code to be multiplexed as masks 801,901 asshown in FIG. 8 and FIG. 9. FIG. 8 is a drawing showing a state in whicha search code and control channel signal are time-multiplexed. In thiscase, the control channel signal and masks can use different or sameshort codes. FIG. 9 is a drawing showing a state in which a search codeand control channel signal are code-multiplexed. In this case, thecontrol channel signal and masks must use different short codes.

As shown in FIG. 8, if the search code and control channel signal aretime-multiplexed, they are not overlapped on a same time zone, andtherefore same short codes can be shared. If the search code and controlchannel signal are code-multiplexed, a new short code must be providedfor the search code, but multiplexing and transmission power control ofsearch codes can be performed independently of control channels.

In accordance with the above description of FIGS. 3 and 8, multiplexingcomponent 308, 309, 310 multiplexes a search code (CSC and GIC _(j)added together at 307 ) with a first control channel signal, of saidplurality of control channel signals, output from 304 and a secondcontrol channel signal, of said plurality of control channel signals,output from 306 at a specific timing as illustrated for example in FIGS.8 and 9. Each of FIGS. 5 and 10 includes a similar multiplexingcomponent, as described in detail below.

The present embodiment explains a case as shown in FIG. 6 where thesearch code multiplexing section has a configuration in which themultiplexing destination of a search code is switched in such a way thata plurality of codes (two codes here) are multiplexed in synchronizationwith the control channel signal (configuration for transmitting searchcodes from a same antenna). With such a configuration, if one code isused as a known signal to estimate channels, it is possible to detectanother code using the result of channel estimation even if that codehas been subjected to data modulation and transmitted.

Furthermore, the search code multiplexing section can also have aconfiguration shown in FIG. 7, that is, a configuration in which themultiplexing destination of a search code is switched in such a way thata plurality of codes are multiplexed independently of the controlchannel signal (configuration for transmitting search codes fromdifferent antennas). That is, the search code multiplexing section canhave a configuration comprising switch 701 for independently switchingthe multiplexing destination of short code CSC, switch 702 forindependently switching the multiplexing destination of groupidentification code GICJ and adders 703,704 that add up short code CSCand group identification code GICj. These switches 701,702 arecontrolled by a transmission antenna switching control signal.

Such a configuration allows mask multiplexing to be performed at varioustimings, increasing variations in mask multiplexing. Furthermore, evenif transmission power of search codes is strong compared to transmissionpower of control channels, this configuration can prevent a plurality ofsearch codes from transmitting from a same antenna simultaneously,enabling the peak factor requested by a transmission amplifier toreduce.

The transmission apparatus of the present embodiment switches thetransmission antenna of search cods so that search codes may betransmitted only through one antenna in a given instant. In this case,switching can be performed either periodically or randomly. That is, itis only search codes that are transmitted using TSTD. However,transmission power of search codes is controlled independently ofcontrol channels.

This allows transmission diversity effects to be demonstrated not onlyfor control channels but also for search codes, making them moreresistant to fading variations, especially fading variations andshadowing during slow movement and improving reception characteristicson the receiving side. Furthermore, the transmission apparatus of thepresent embodiment can reduce the number of correlators such as matchedfilters required for a cell search, making it possible to improvereception characteristics and simplify the configuration of theapparatus.

Since the transmission diversity system for control channels isdifferent from that for search codes, with different effects obtainedand different required reception characteristics, transmission power ofsearch codes may be controlled independently of that of controlchannels. For example, even if control channels are transmitted with 50%power (0.5) through parallel transmission by two channels, search codesmay be transmitted with the same power (1) as in the case of one searchcode.

(Embodiment 2)

The present embodiment explains a case where OTD (Orthogonal TransmitDiversity), a mode of parallel transmission, is used. OTD refers to atechnology by which a transmission signal is converted from serial toparallel, data-modulated and spread-modulated, and each transmitted inparallel from different antennas while maintaining orthogonality.

FIG. 4 is a block diagram showing the configuration of an apparatuscarrying out OTD in Embodiment 2 of the present invention. Thisapparatus converts transmission data to parallel through a plurality(two in the figure) of systems through serial/parallel conversionsection 401, modulates the data through data modulation sections402,403, spread-modulates through spread-modulation sections 404,405,carries the data on carriers through radio transmission circuits 406,407and transmits through antennas 408,409.

Then, a transmission apparatus of the present embodiment is explainedusing FIG. 5. FIG. 5 is a block diagram showing the configuration of thetransmission apparatus in a base station apparatus according toEmbodiment 2 of the present invention.

This transmission apparatus enables parallel transmission using twosystems and comprises serial/parallel conversion section 501 thatconverts control channel signals from serial to parallel, datamodulation circuits 502,503 that perform data modulation on a controlchannel (e.g., perch channel) signal, multipliers 505,507 that multiplythe demodulated signal by a specific coda, multipliers 504,506 thatmultiply long code LCj and short codes SC0,SC1 respectively, a searchcode providing section that provides search codes, and a search codemultiplexing section that multiplexes the search codes using switches509,510,511 that are the switching sections to switch the multiplexingdestination of search codes.

The search code providing section comprises adder 508 that adds up shortcode CSC and group identification code CICj and the search codemultiplexing section comprises switches 509,510,511 that multiplex theadded code over one control channel signal as a mask.

Then, the operation of the transmission apparatus configured as shownabove is explained.

The control channel signal is converted from serial to parallel byserial/parallel conversion section 501, input to two data modulationcircuits 502,503 and subjected to data modulation processing. Inmultipliers 504,506, long code LCj and short codes SC0,SC1 aremultiplied. These multiplied long code LCj and short code SC0 aremultiplied on the output of data modulation circuit 502 by multiplier505 and long code LCj and short code SC1 are multiplied on the output ofdata modulation circuit 503 by multiplier 507.

In the base station apparatus with this transmission apparatus, forexample, a long code LCj assigned differs from one base station toanother. As described above, control channel signals are dually spreadwith long code LCj and short code SC. This allows each base station touse a common short code group.

On the other hand, in the search code providing section, short code CSCand group identification code GICj are added up by adder 508 and themultiplexing section multiplexes them over one control channel signal byswitching of switch (TSW) 509. Switching of switch 509 is controlled bytransmission antenna switching control signal 513.

Switch (SW0) 510 and switch (SW1) 511 turn ON at a prescribed timing andaforementioned short code CSC and group identification code GICj aremultiplexed over the control channel signal at that timing.

Therefore, if switch TSW 509 turns ON at a timing of the waveform inFIG. 5, that is, it is selected as the multiplexing destination,switches SW0 and SW1 turn ON at a timing of the waveform in FIG. 5 andshort code CSC and group identification code GICj are multiplexed overthe control channel signal. These switches SW0 and SW1 are controlled bymask control signal 512. That is, switches SW0 and SW1 are controlled sothat short code CSC and group identification code GICj may bemultiplexed over any one control channel signal at a specific timing.Such control allows a search code to be multiplexed as masks 801,901 asshown in FIG. 8 and FIG. 9.

The present embodiment explains a case as shown in FIG. 5 where thesearch code multiplexing section has a configuration in which themultiplexing destination of a search code is switched in such a way thata plurality of codes (two codes here) are multiplexed in synchronizationwith the control channel signal. Furthermore, the search codemultiplexing section can also have a configuration shown in FIG. 7, thatis, a configuration in which the multiplexing destination of a searchcode is switched in such a way that a plurality of codes are multiplexedindependently of the control channel signal. This configuration isexplained in detail in Embodiment 3.

The transmission apparatus of the present embodiment switches thetransmission antenna of search cods so that search codes may betransmitted only through one antenna in a given instant. In this case,switching can be performed either periodically or randomly. That is, itis only search codes that are transmitted using TSTD.

In this case, the amount of transmission data is reduced to a fractionof the original amount divided by the number of antennas, and thereforewhen transmitting using the same band, the spreading factor can bemultiplied by the number of antennas. For example, in the case of x64spreading with one antenna, the spreading factor becomes x128 with twoantennas. The spreading codes used for spread-modulation are mutuallyorthogonal (called “orthogonal codes”). Therefore, even if transmissionpower of each antenna is reduced to a fraction of the amount divided bythe number of antennas, spreading gain (process gain) by despreading ismultiplied by the number of antennas, and therefore the basiccharacteristic of each antenna remains the same as that for one antenna.

Furthermore, according to the transmission apparatus of the presentembodiment, signals converted from serial to parallel are eachtransmitted from different antennas through different paths, andtherefore it is possible to reduce concentration errors during slowfading such as burst errors and deterioration by shadowing (slowvariations of reception power due to tree and building shadows) comparedto transmission using one antenna.

When the transmission apparatus of the present embodiment performs errorcorrection encoding on transmission data, then converts them from serialto parallel and transmits from respective antennas, and the receivingside detects each transmitted signal, converts it from parallel toserial, then performs error correction decoding, it is especiallyeffective because it allows a drastic improvement of receptioncharacteristics.

The transmission apparatus of the present embodiment can further reducethe number of correlators such as matched filters required for a cellsearch on the receiving side, making it possible to improve receptioncharacteristics and at the same time simplify the apparatusconfiguration.

Since the transmission diversity system for control channels isdifferent from that for search codes, with different effects obtainedand different required reception characteristics, transmission power ofsearch codes may be controlled independently of that of controlchannels. For example, even if control channels are transmitted with 50%power (0.5) through two OTDs, search codes may be transmitted with thesame power (1) as in the case of search codes.

(Embodiment 3)

The present embodiment explains a case where transmission diversity iscarried out in such a way that short code (CSC) and short code (GICj)are not transmitted from a same antenna simultaneously.

In some CDMA radio communication systems, transmission power of searchcodes may be stronger than that of control channels. At this time, ifswitching is performed so that a plurality of search codes may bemultiplexed in synchronization with one control channel, extremely hightransmission peak power is required at the transmission timing of searchcodes. Meeting this requirement requires the use of an expensive poweramplifier with a large dynamic range. It is therefore desirable toreduce the peak factor required for the transmission amplifier of thetransmission apparatus.

The present embodiment explains a case where OTD, a mode of paralleltransmission, is used. FIG. 10 is used to explain the transmissionapparatus of the present embodiment. FIG. 10 is a block diagram showingthe configuration of a transmission apparatus of a base stationapparatus according to Embodiment 3 of the present invention. Thetransmission apparatus shown in FIG. 10 is a combination of thetransmission apparatus in FIG. 5 and the switching section in FIG. 7.

That is, this transmission apparatus enables OTD transmission by twosystems and comprises serial/parallel conversion section 501 thatconverts a control channel signal from serial to parallel, datamodulation circuits 502,503 that perform data modulation on a controlchannel (e.g., perch channel) signal, multipliers 505,507 that multiplythe modulated signal by a specific code, multipliers 504,506 thatmultiply long code LCj and short codes SC0,SC1 respectively, a CSCgenerator that generates short code CSC which is a search code, a GICjgenerator that generates group identification code GICj which is also asearch code, switches 701,702 that are the switching sections to switchthe multiplexing destination of search codes, and switches (SW0) 510 and(SW1) 511 that switch between a spread-modulated signal and search codeand time-multiplex them.

Then, the operation of the transmission apparatus configured as shownabove is explained.

Control channel signals are converted from serial to parallel byserial/parallel conversion section 501, input to data modulationcircuits 502,503 where they are subjected to data-modulation processing.In multipliers 504 and 506, long code LCj and short codes SC0,SC1 aremultiplied. These multiplied long code LCj and short code SC0 aremultiplied on the output of data modulation circuit 502 by multiplier505 and long code LCj and short code SC1 are multiplied on the output ofdata modulation circuit 503 by multiplier 507.

In the base station apparatus provided with this transmission apparatus,for example, a long code LCj assigned differs from one base station toanother. As described above, control channel signals are dually spreadwith long code LCj and short code SC. This allows each base station touse a common short code group.

On the other hand, short code CSC and group identification code GICJ areswitched at a specific timing by interlocked switches (TSW) 701,702 andtransmitted from different antennas. Therefore, the multiplexingdestinations are controlled in such a way that search codes sent fromthose antennas are always switched.

Switch (SW0) 510 and switch (SW1) 511 turn ON at a prescribed timing andaforementioned short code CSC and group identification code GICj aremultiplexed over the control channel signal at the same timing.

Therefore, if switches (TSW) 701,702 turn ON at a timing of the waveformin FIG. 10, that is, if SW0 for CSC and SW1 for CICj are selectedrespectively as the multiplexing destinations, switches SW0 and SW1 turnON at a timing of the waveform in FIG. 10 and short code CSC and groupidentification code GICj are multiplexed over the control channelsignal.

These switches SW 701,702 are controlled by transmission antennaswitching control signal 705 and switches SW0 and SW1 are controlled bymask control signal 512. That is, switches SW0,SW1 are controlled sothat short code CSC and group identification code GICj may bemultiplexed over any one control channel signal at a specific timing,and switches SW 701,702 are controlled so that search codes to bemultiplexed over each control channel may be switched every time.

An example of the multiplexed signal during the aforementioned operationis shown in FIG. 11. In FIG. 11, suppose control channels aretransmitted with No. 0 (TS0) and No. 8 (TS8) as CCH slots in a 10 msframe consisting of 16 slots. In these TS0 and TS8, CSC and CICj aretransmitted from different antennas, antenna A and antenna B, and CSCand CISj are transmitted by changing their transmission antennas from Ato B to A and from B to A to B, respectively.

According to the transmission apparatus of the present embodiment, eachsearch code is transmitted from a different antenna at everytransmission timing, making it possible to obtain transmission diversityeffects. Furthermore, when transmission power of search codes isstronger than that of control channels, the present embodiment canprevent a plurality of search codes from being transmitted from a sameantenna simultaneously, reducing the peak factor required by atransmission amplifier.

When transmitting short code CSC and short code GICj from differentantennas, the channel for transmitting search codes and the controlchannel may be different. This status is shown in FIG. 12 and FIG. 13.

In the case shown in FIG. 12, in antenna A, short code CSC and thecontrol channel signal are code-multiplexed and transmitted at TS0 andshort code GICj and the control channel signal are code-multiplexed andtransmitted at TS8.

On the other hand, in antenna B, short code GICJ and the control channelsignal are code-multiplexed and transmitted at TS0 and short code CSCand the control channel signal are code-multiplexed and transmitted atTS8.

In such a code-multiplexing transmission mode, each search code istransmitted from a different antenna at every transmission timing,making it possible to obtain transmission diversity effects.Furthermore, when transmission power of search codes is stronger thanthat of control channels, the present embodiment can prevent a pluralityof search codes from being transmitted from a same antennasimultaneously, reducing the peak factor required by a transmissionamplifier.

In the case shown in FIG. 13, the transmission mode iscode-multiplexing, but search codes CSC and GICj are not multiplexedwith the control channel signal and transmitted. That is, short codesCSC and GICj are transmitted from antennas A and B alternately at TS0and TS8, while the control channel signal is transmitted at TS3 andTS11. Thus, the present embodiment is also applicable in a system usingthe dynamic channel assignment system that enhances the degree offreedom of the channel position.

As shown above, when a variable transmission timing is used for controlchannel signals to enhance the degree of freedom of slot assignment,each search code is transmitted from a different antenna at everytransmission timing, making it possible to obtain transmission diversityeffects. Furthermore, when transmission power of search codes isstronger than that of control channels, the present embodiment canprevent a plurality of search codes from being transmitted from a sameantenna simultaneously, reducing the peak factor required by atransmission amplifier.

The present invention is not limited to Embodiments 1 to 3 above, butcan be modified and implemented in various manners.

Embodiments 1 to 3 above explain the cases where different short codesare used for long codes, short code SC and group identification code GICto be multiplied and short code CSC to be added, but the presentinvention can also be implemented by using same short codes for longcodes, short code SC and group identification code GIC to be multipliedand short code CSC to be added.

As explained above, the transmission apparatus in the present inventionmakes control channels more resistant to fading variations (especiallyduring slow movement) and shadowing through transmission diversityeffects by parallel transmission including OTD, improving receptioncharacteristics. It also allows switching transmission diversity effectsto be demonstrated on search codes, making them more resistant to fadingvariations, especially fading during slow movement and shadowing,improving reception characteristics on the receiving side.

The transmission apparatus in the present invention can further obtaindiversity effects without increasing the number of codes required forsearch codes per sector nor the receiving side increasing the number ofmatched filters required for search codes. This makes it possible toimprove search code reception characteristics and improve initialsynchronization characteristics.

The present invention is not limited to the above described embodiments,and various variations and modifications may be possible withoutdeparting from the scope of the present invention.

This application is based on the Japanese Patent Application No.HEI10-157405 filed on Jun. 5, 1998 and the Japanese Patent ApplicationNo. HEI11-051059 filed on Feb. 26, 1999, entire content of which isexpressly incorporated by reference herein.

1. A transmission apparatus comprising: a search code provider thatprovides a search code to be used for cell search; a plurality oftransmission sections that transmit a plurality of control channelsignals in parallel; and a multiplexer that multiplexes said search codewith a first control channel signal of said plurality of control channelsignals at a specific timing, wherein said multiplexer switches frommultiplexing said search code with said first control channel signal tomultiplexing said search code with another control channel signal ofsaid plurality of control channel signals over time.
 2. The transmissionapparatus according to claim 1, wherein said multiplexer multiplexes thesearch code alternately with the plurality of control channel signals.3. The transmission apparatus according to claim 1, wherein saidtransmission apparatus uses an orthogonal transmission diversitytechnique.
 4. The transmission apparatus according to claim 1, whereinsaid multiplexer time-multiplexes the search code with the plurality ofcontrol channel signals.
 5. The transmission apparatus according toclaim 1, wherein said multiplexer code-multiplexes the search code withthe plurality of control channel signals.
 6. The transmission apparatusaccording to claim 1, wherein said search code provider provides aplurality of codes as the search code, and said multiplexer multiplexesseparately the plurality of codes with the plurality of control channelsignals.
 7. The transmission apparatus according to claim 1, whereinsaid search code provider provides a plurality of codes as the searchcode, and said multiplexer multiplexes in synchronization the pluralityof codes with the plurality of control channel signals.
 8. A basestation apparatus comprising a transmission apparatus comprising: asearch code provider that provides a search code to be used for cellsearch; a plurality of transmission sections that transmit a pluralityof control channel signals in parallel; and a multiplexer thatmultiplexes said search code with a first control channel signal of saidplurality of control channel signals at a specific timing, wherein saidmultiplexer switches from multiplexing said search code with said firstcontrol channel signal to multiplexing said search code with anothercontrol channel signal of said plurality of control channel signals overtime.
 9. A transmission method used in a CDMA radio communicationsystem, comprising: (a) providing a search code to be used for cellsearch; (b) transmitting a plurality of control channel signals inparallel; and c) multiplexing said search code with a first controlchannel signal of said plurality of control channel signals at aspecific timing, and switching from multiplexing said search code withsaid first control channel signal to multiplexing said search code withanother control channel signal of said plurality of control channelsignals over time.
 10. The transmission apparatus according to claim 1,wherein said multiplexer multiplexes the search code with said anothercontrol channel signal at a specific timing which is different from saidspecific timing that said multiplexer multiplexes said search code withsaid first control channel signal.
 11. The transmission apparatusaccording to claim 8, wherein said multiplexer multiplexes the searchcode with said another control channel signal at a specific timing whichis different from said specific timing that said multiplexer multiplexessaid search code with said first control channel signal.
 12. Thetransmission apparatus according to claim 9, wherein said multiplexermultiplexes the search code with said another control channel signal ata specific timing which is different from said specific timing that saidmultiplexer multiplexes said search code with said first control channelsignal.
 13. A transmission apparatus comprising: a search code providerthat provides a search code to be used for cell search; a plurality oftransmission sections that transmit a plurality of control channelsignals in parallel; and a multiplexing component that multiplexes saidsearch code with a first control channel signal and a second controlchannel signal of said plurality of control channel signals at aspecific timing, wherein said first control channel signal and saidsecond control channel signal are alternatively transmitted over time.14. The transmission apparatus according to claim 13, wherein saidtransmission apparatus uses an orthogonal transmission diversitytechnique.
 15. The transmission, apparatus according to claim 13,wherein said multiplexer time multiplexes the search code with theplurality of control channel signals.
 16. The transmission apparatusaccording to claim 13, wherein said multiplexer code multiplexes thesearch code with the plurality of control channel signals.
 17. Thetransmission apparatus according to claim 13, wherein said search codeprovider provides a plurality of codes as the search code, and saidmultiplexer multiplexes separately the plurality of codes with theplurality of control channel signals.
 18. The transmission apparatusaccording to claim 13, wherein said search code provider provides aplurality of codes as the search code, and said multiplexer multiplexesin synchronization the plurality of codes with the plurality of controlchannel signals.
 19. A base station apparatus comprising a transmissionapparatus comprising: a search code provider that provides a search codeto be used for cell search; a plurality of transmission sections thattransmit a plurality of control channel signals in parallel; and amultiplexing component that multiplexes said search code with a firstcontrol channel signal and a second control channel signal of saidplurality of control channel signals at a specific timing, wherein saidfirst control channel signal and said second control channel signal arealternatively transmitted over time.
 20. The transmission apparatusaccording to claim 13, wherein said multiplexer multiplexes the searchcode with said another control channel signal at a specific timing whichis different from said specific timing that said multiplexer multiplexessaid search code with said first control channel signal.
 21. Atransmission method used in a spread spectrum radio communicationsystem, comprising: (a) providing a code to be used for cell search; (b)transmitting a first parallel signal, wherein the first parallel signalcorresponds to a first control channel signal multiplexed with the code;and (c) transmitting a second parallel signal, wherein the secondparallel signal corresponds to a second control channel signalmultiplexed with the code; wherein the first and second parallel signalsare transmitted utilizing time switched transmit diversity.
 22. Thetransmission apparatus according to claim 21, wherein said multiplexermultiplexes the search code with said another control channel signal ata specific timing which is different from said specific timing that saidmultiplexer multiplexes said search code with said first control channelsignal.
 23. A transmission method used in a spread spectrum radiocommunication system, comprising: (a) providing a code to be used forcell search; (b) periodically transmitting a first signal through afirst antenna, wherein the first parallel signal corresponds to a firstcontrol channel signal multiplexed with the code; and (c) alternativelytransmitting a second signal through a second antenna over time, whereinthe second parallel signal corresponds to a second control channelsignal multiplexed with the code.
 24. An apparatus comprising: areception device for obtaining a parallel signal from a base stationapparatus, wherein the base station apparatus comprises: (a) a searchcode provider that provides a search code to be used for cell search;(b) a plurality of transmission sections that transmit a plurality ofcontrol channel signals in parallel; and (c) a multiplexing componentthat multiplexes said search code with a first control channel signaland a second control channel signal of said plurality of control channelsignals at a specific timing, wherein said first control channel signaland said second control channel signal are alternatively transmittedover time.